Norman Baker: Our task as Members of Parliament is to regain the trust of the electorate

How can it be right to charge the taxpayer for oil paintings, goldfish bowls and pot plants?

Another day, another terrible set of headlines for MPs and for Parliament. How long can this corrosive saga continue?

The basic problem is this: claims for expenses should reflect expenditure legitimately and necessarily incurred by a Member of Parliament as part of his or her duties – no more, no less. Instead, they have been used by too many MPs as an alternative income stream, as a way of bumping up salary without having to vote through an embarrassing increase.

It is quite wrong that MPs should be taking out mortgages with money provided by the taxpayer, then pocketing the capital gain when the property is sold. It is even worse when they regularly change the designation of their second home in order to maximise the income they can generate through the allowance system.

Does the Home Secretary not realise how wrong it looks to the average person when she calls her sister's spare room her main home, while running up bills at taxpayers' expense for her real home, where her family lives?

And how can it be right to charge the taxpayer for oil paintings, goldfish bowls, pot plants, and mock Tudor beams?

The standard defence trotted out is that everything done has been within the rules. But that does not make it ethically correct, not least because those rules have been written by MPs themselves.

And so we have the unedifying spectacle of Peter Mandelson, who after all knows a thing about houses, claiming £3,000 to improve his house less than a week after he announced his intention to stand down as an MP. Within the rules? Yes. Defensible? No.

The next two or three months are going to be truly awful for MPs. There will be more revelations, more outrage. That cannot now be avoided.

But MPs must ensure that when the outrage has subsided, they repair the damage with new rules that limit claims to rent and other running expenses, with every claim subject to complete transparency and external audit. The test will be this: can we walk into our local pub or supermarket and feel comfortable defending what we claim. Until the public think the answer is yes, this corrosive matter will not go away, and nor should it.